I love roasted stuffed portabellas, and I love poached eggs - they make just about anything better. For this recipes I borrowed technique from Merrill's recipe for Will's mushrooms, roasting and flipping the mushrooms, which works beautifully. —aargersi
Preheat the oven to 375. Place an oven safe rack on top of a cookie sheet and spray it with no-stick or lightly brush it with oil.
Brush the mushrooms clean and remove the stem and the gills (I use a soup spoon to gently scrape them out). Lightly season the inside with salt and pepper and place gill side down on the rack. Bake for about 20 minutes - they should still be a bit firm as you want them to stand up to being filled.
Meanwhile, mix the two cheeses and the rosemary in a bowl. Using a zester or microplane, grate the garlic first then zest the lemon - the lemon peel will push the garlic out of the microplane - otherwise it tends to want to stick there. You should also now bring a pot of water to the boil for your eggs, add a good amount of salt and a splash of white vinegar.
Pull the mushrooms out of the oven and flip them. You may need to drain some liquid off the cookie sheet. Turn the oven up to 425. Fill each cap with equal amounts of the cheese mixture, grind some pepper over the top and put them back on the rack and back into the oven. Bake them until the cheese is melted and bubbling. Right before you pull the mushrooms out of the oven, poach your eggs - this takes about 3-4 minutes.
Place the mushrooms on a plate or plates (depending if you are sharing or not) and gently put a well drained poached egg on top of each. Sprinkle fresh chives on top and serve!